Bbecca, I’ve seen two-week-old chicks fly up two feet and horizontal three feet. From watching it was obvious they could have gone a lot further if they wanted to. They were different breeds than yours but the same general size breeds. You do not have to worry about them falling. They may not even use those ramps, thy may just fly up or down.
I don’t know what your brooder looks like but the only reason I can think of to stop you from just opening the brooder door and walking away is if you have older chickens and you are worried about integration. If you don’t have older chickens, I can’t think of any reason to keep them locked up.
They have been in that brooder for a while so it is home. Sometimes chickens are afraid of change. It’s possible every one of them could be out of the brooder and in the coop within a few minutes of you opening that door. It’s possible it could take a couple of days before they build up the courage to leave the safety of the brooder. Both are normal reactions. Just open the door and walk away. They will manage. Of course, there is nothing wrong with checking on them occasionally, or maybe regularly.
I have no idea where they will sleep at night. They may go back into the brooder, especially if it is on the coop floor. They may go somewhere else to sleep, especially if the brooder is elevated. Until they start roosting at night, mine tend to like to sleep in lower spots. But yours could be different. About the only thing consistent with chicken behavior is that they are inconsistent. Each brood is unique and may not follow the rules.
There is nothing wrong with leaving that lamp on for a while. If they need the heat, they’ll go to it. If they don’t they may not. It’s possible, maybe even probable, that they will continue to sleep where they always have as long as you don’t remove the brooder. There is no magic age to remove the heat source. One summer in temperatures a lot warmer than yours I turned the daytime heat off at 2 days, the overnight heat off at 5 days. Their body language told me they did not need the heat. In winter I sometimes leave the heat on until 5 weeks. Even with overnight lows at or below freezing mine don’t need it after that. My brooder is 3’ x 6’ and is also in the coop.
From my experience and what you have described, you are good to go.